Development Of High Strength Concrete Research Articles

Effect of curing regime on the strength development and microstructure evolution of high strength concrete

Autoclaved curing can increase the compressive strength of high strength concrete (HSC) element at early age, but it has a negative impact on the properties of the concrete at long-term service due to the “thermal-damage effect”. This study aims to identify a suitable curing regime for HSC on the premise of ensuring early strength requirements and production efficiency. The influence of six different curing regimes on the strength development of HSC was investigated, and the hydration products of the binder, morphology and pore structure of the concrete were also explored. Results showed that enclosed curing at room temperature in the summer season and hydrothermal curing at 35 °C promoted the early strength development of concrete, and the compressive strength at 1 day exceeded 60 MPa. Continuous strength gain occurred at later age, with a value of 107.9 MPa at 28 day. It was ascribed to the fact that hydration products under these conditions refined the pore structure to produce a denser structure. Hydrothermal curing at 60 °C contributed the strength development at super early age (e.g. 10 hours), but the strength at late age was reduced due to the delayed formation of ettringite and the deterioration of pore structure. Autoclaved curing resulting in the uneven distribution of hydration products and the poor distribution of pore size was not recommended.

A study on the role of metakaolin and alccofine as supplementary materials on strength properties of concrete

In recent years, the utilization of supplementary materials has played an important role in development of high strength concrete, improving the overall properties of concrete and rendering sustainability to concrete construction. Though different supplementary materials such as fly ash, silica fume, metakaolin and ground granulated blast furnace slag have been utilized for development of concrete, there is a need to understand the comparative role of these supplementary materials on workability, early strength gain, stress–strain response under compression and flexure, etc. In this context, the present study evaluates the comparative performance of metakaolin and alccofine (ultrafine slag) as supplementary materials in concrete; wherein, 30% replacement of cement with supplementary cementitious has been done (20% replacement with fly ash (class C) and 10% replacement with metakaolin, MK / alccofine, AL). The comparative assessment of the compressive strength, stress–strain behaviour and flexural response of MK- and AL- blended concrete has been carried out, and the results suggests that AL blended concrete exhibits higher early age strength (7 days curing), as compared to MK blended concrete. Similar trend in strength development is witnessed for 28 days and 56 days cured specimen; wherein, the average 56 days compressive strength of AL blended concrete observed to be 86.11 MPa, is substantially higher than 61.45 MPa strength observed for MK blended concrete (load control tests). Further, the flexural strength of AL blended concrete is noted to be higher than MK blended concrete. Moreover, the pre-peak and post-peak energy absorption capacity, evaluated from stress-strain (displacement control compression tests) and load–displacement response (flexural tests) of AL blended concrete, is higher than MK blended concrete, indicating its higher ductility under loading. Overall, the study findings suggest the beneficial contribution of supplementary materials in developing sustainable concrete with superior properties, and demonstrates the potential of AL as supplementary material in concrete.

Strength Development of High Strength Concrete using Rice Husk Ash

Strength Development of High Strength Concrete using Rice Husk Ash

Influence of Curing Practices and Environment on Compressive Strength De-velopment of High Strength Concrete

The paper presents the impact of practicing curing techniques on the compressive strength evolution of ternary blended high strength concrete under local prevailing environmental conditions. Initially the control mix was designed using the guidelines of IS: 10262:2009, whose compressive strength at 28 days is greater than 70 MPa. Later mechanical properties of high strength concrete after incorporating the alternative binder materials was evaluated. For all mixtures water to cement ratio was kept as 0.25. For the purpose of improving the mechanical properties of control mix and to achieve the economy slag, fly ash, quartz powder and silica fume were incorporated in the mix as partial substitution of cement. Total replacement with supplementary binders was kept at 20% by its weight of cement. Among all the combinations, silica fume and slag combination performed well in respect to the hardened properties. Subsequently, the same mix was considered in order to study the influence of practicing curing methods. From the results it was concluded that although type of curing regime on strength development both in indoor and outdoor environment at early ages was not considerable but at the later ages the effect was considerable. Compressive strength of specimens subjected to sprinkling, burlap and plastic cover curing in outdoor environment are significantly affected than the corresponding specimens in indoor environment.

Study on Mechanical Properties of Concrete by Fractional Replacement of Cement with Metakaolin and Sand with M-Sand by Using M30 Grade

Metakaolin (MK) is a mineral admixture, various tests are carried out on the usage of Metakaolin for the development of high strength concrete. MK is a supplementary cementitious material derived from heat treatment of natural deposits of kaolin. Metakaolin exhibits high pozzolana reactivity due to their amorphous structure and high surface area. Concrete is the most commonly used material for development of infrastructure. As infrastructure is growing there arises problems in repairs. Due to manufacture of cement, Co2gets emitted into environment. Researches started on working partial replacement of cement, which occur naturallyor manufactured. The different type of pozzolonic materials like metakaolin, silica fume, and fly ash etc, are the material have binding properties that of cement. The present study focuses on replacement cement with metakaolin by 0, 5, 10,15and 20% and fine aggregate with M-sand by 50%.

Reactivity Index and Strength Development of High Strength Concrete with GGBFS Cement

The slag cement industry in Indonesia is growing in tandem with the smelter industry as a supplier of slag material. The use of slag cement instead of ordinary cement can reduce CO2 emissions. This research aimed to design the mixture composition of slag cement and ordinary cement for high-strength concrete. Standard concrete cylinders and concrete beams were tested to gain the compressive, tensile and flexural strength. The testing results indicate that generally, the concrete mixture compositions of low GGBFS (25%) gained their optimum strength at the age of 28 days while concrete with high composition of GGBFS (55%) achievedsimilar strength at the age of 90 days.A mixture using higher percentage replacement of GGBFS might attain its optimum strength at the longer ages. The use of Silica Fume (SF) in high-strength concrete mixtures with GGBFS found ineffective to increasethe concrete strength as the results indicate that concretes with SF have lower strength compared with non-SF concrete mixtures.

Performance of High-strength Concrete Made with Recycled Ceramic Aggregates (Research Note)

Recent scientific concerns to achieve sustainability in construction have suggested the implementation of using recycled aggregate in concrete; because it has the potential to reduce the demand for extraction of natural raw materials and decrease the volume of wastes landfilled. In this respect, this study aims to investigate the suitability of using ceramic tile (CT) and ceramic sanitary (CS) wastes as coarse aggregate in production of high-strength concrete (HSC). Different concrete mixes were produced by partial replacement of 10, 20 and 30% of natural coarse aggregate with recycled aggregates. Besides investigating the characteristics of recycled aggregate, slump, compressive strength, initial and final absorption and chloride ion penetration depth of HSC specimens were evaluated and compared with that of plain HSC. Results showed that using recycled ceramic aggregates increased the superplasticizer dosage to maintain the target slump. Although by incorporation of high percentage of CT or CS aggregate, compressive strength of HSCs was reduced compared with reference HSC, it is possible to produce HSC with 28-days compressive strength higher than 60.7 MPa. Moreover, the absorption and chloride ion penetration depth of recycled aggregate incorporated HSC were higher than those of estimated for plain concrete. Generally, waste ceramic aggregate at optimum replacement ratio can be used in the sustainable development of HSC.

Development of Alkaline Activated High Strength Concrete using Fly Ash - Ground Granulated Blast Furnace Slag - Metakaolin as Binders and Manufacturing Sand as Fine Aggregate

Structures built with normal concrete are fading out from the construction industry due to the development of high strength concrete. The massive structures such as sky scrapers, bridges, tunnels, nuclear plants, underground structures need high strength concrete to withstand the high intensity vertical, horizontal and moving loads etc. The development of high strength alkaline activated concrete will reduce the usage of cement in construction community. Lesser the utilisation of cement will lessen the high emission of carbon dioxide gas into the atmosphere. In this study, high strength concrete using alumina and silica rich materials are made with a mix ratio of 1:1.31:2.22. The water to cement ratio for high strength cement concrete and the alkaline solution to binder ratio for alkaline activated concrete are kept as 0.35. Low calcium fly ash, Ground Granulated Blast Furnace Slag (GGBS) and Metakaolin are used as binders and Manufacturing Sand is used as fine aggregate to made high strength alkaline activated concrete. The high strength alkaline activated concrete tests results are better than the high strength cement concrete.

초기 양생조건에 따른 고강도 콘크리트의 강도발현에 관한 실험적 연구

본 연구는 PC부재의 공장생산에 있어서 여러 가지 증기양생 조건의 변수에 따른 고강도 콘크리트의 초기 압축강도 발현성상을 실험적으로 검증하고, 최적 양생조건을 확인하기 위한 것이다. 40 MPa 이상의 고강도 콘크리트 제조에는 보통 포틀랜드 시멘트를 사용하였으며, 콘크리트의 배합조건은 물-시멘트비 3종류(W/C 25%, 35% 및 45%)를 대상으로 하였다. 본 연구의 증기양생 변수로 (1) 전치양생 시간 3종류, (2) 최고 양생온도 3종류, (3) 최고온도 유지시간 3종류, (4) 승온 및 강온양생 온도 1종류 등을 대상으로 재령별 압축강도 시험을 실시하였다. 또한, 증기양생 및 표준양생에 따른 재령별 강도발현을 비교하였다. 실험결과, (1) 전치양생은 콘크리트의 초기 응결시간 이상, (2) 최고 양생온도는 55°C 이하, (3) 최고온도 유지시간은 6시간 이하로 하는 것이 증기양생 고강도 콘크리트의 강도발현에 적합한 양생조건으로 나타났다. 또한, 재령 28일에서 증기양생과 표준양생의 압축강도 발현성상의 역전현상이 발생하였다. 따라서 이러한 양생조건으로 PC부재의 생산성 및 현장관리를 위한 기초자료로 제시하고자 한다.

Developing Sustainable High Strength Concrete Mixtures Using Local Materials and Recycled Concrete

This study presents the development of high strength concrete (HSC) that has been made more sustainable by using both local materials from central Texas and recycled concrete aggregate (RCA), which has also been obtained locally. The developed mixtures were proportioned with local constituents to increase the sustainable impact of the material by reducing emissions due to shipping as well as to make HSC more affordable to a wider variety of applications. The specific constituents were: limestone, dolomite, manufactured sand (limestone), locally available Type I/II cement, silica fume, and recycled concrete aggregate, which was obtained from a local recycler which obtains their product from local demolition. Multiple variables were investigated, such as the aggregate type and size, concrete age (7, 14, and 28-days), the curing regimen, and the water-to-cement ratio (w/c) to optimize a HSC mixture that used local materials. This systematic development revealed that heat curing the specimens in a water bath at 50℃ (122oF) after demolding and then dry curing at 200℃ (392oF) two days before testing with a w/c of 0.28 at 28-days produced the highest compressive strengths. Once an optimum HSC mixture was identified a partial replacement of the coarse aggregate with RCA was completed at 10%, 20%, and 30%. The results showed a loss in compressive strength with an increase in RCA replacement percentages, with the highest strength being approximately 93.0 MPa (13,484 psi) at 28-days for the 10% RCA replacement. The lowest strength obtained from an RCA-HSC mixture was approximately 72.9 (MPa) (10,576 psi) at 7-days. The compressive strengths obtained from the HSC mixtures containing RCA developed in this study are comparable to HSC strengths presented in the literature. Developing this innovative material with local materials and RCA ultimately produces a novel sustainable construction material, reduces the costs, and produces mechanical performance similar to prepackaged, commercially, available construction building materials.

Influence of Silica Fume Inclusion on the Compressive Strength Development of High Strength Concrete Containing High Volume of Palm Oil Fuel Ash

The influence of silica fume (SF) inclusion on the compressive strength development of high strength concrete (HSC) containing high volume of palm oil fuel ash (POFA) has been investigated. A HSC containing 100% ordinary Portland cement (OPC) and another HSC mix with 50% POFA as part of the binder were prepared. Due to the reduction in early strength of the HSC with the inclusion of high volume of POFA in the binary blended binder HSC, attempt was made to partially replace the OPC with SF at 5, 10, 15 and 20%, thus creating a ternary blended binder HSC. The results show that the compressive strength development of the HSC containing high volume of POFA was significantly improved with the inclusion of SF. The ternary blended binder HSC with 15% SF exhibited the highest increase in early age strength, even though it did not surpass the OPC-HSC, and it provided the highest strength at 7 and 28 days in comparison to other HSC mixes. Thus, ternary blended binder containing more than 60% supplementary cementitious material (POFA and SF) could be utilized to produce HSC.

Superplasticizer for High Strength Concrete

ABSTRACTIn the early 1970s, experts predicted that the practical limit of ready-mixed concrete would be unlikely to exceed a compressive strength greater than 90 MPa [1]. Over the past two decades, the development of high-strength concrete has enabled builders to easily meet and surpass this estimate. The primary difference between high-strength concrete and normal-strength concrete relates to the compressive strength that refers to the maximum resistance of a concrete sample to applied pressure. Although there is no precise point of separation between high-strength concrete and normal-strength concrete, the American Concrete Institute defines high-strength concrete as concrete with a compressive strength greater than 45 MPa. Manufacture of high-strength concrete involves making optimal use of the basic ingredients that constitute normal-strength concrete. When selecting aggregates to obtain high-strength concrete, we consider strength, optimum size distribution, surface characteristics and a good bonding with the cement paste that affect compressive strength. Selecting a high-quality Portland cement and optimizing the combination of materials by varying the proportions of cement, water, aggregates, and admixtures is also necessary. Any of these properties could limit the ultimate strength of high-strength concrete. Pozzolans, such as fly ash and silica fume along with silicic acid, are the most commonly used mineral admixtures in high-strength concrete. These materials impart additional strength to the concrete by reacting with Portland cement hydration products to create additional Calcium Silicate Hydrate (CSH) gel, the part of the paste responsible for concrete strength; finally the most important admixture is polycarboxylate ether as super plasticizer. It would be difficult to produce high-strength ready-mixed concrete without using chemical admixtures. In this paper we study the use of high performance concrete (HPC) to obtain very narrow strong pre-fabricated elements for water conducting channels.

Effect of Curing Temperature Histories on the Compressive Strength Development of High-Strength Concrete

This study examined the relative strength-maturity relationship of high-strength concrete (HSC) specifically developed for nuclear facility structures while considering the economic efficiency and durability of the concrete. Two types of mixture proportions with water-to-binder ratios of 0.4 and 0.28 were tested under different temperature histories including (1) isothermal curing conditions of 5°C, 20°C, and 40°C and (2) terraced temperature histories of 20°C for an initial age of individual 1, 3, or 7 days and a constant temperature of 5°C for the subsequent ages. On the basis of the test results, the traditional maturity function of an equivalent age was modified to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. To determine the key parameters in the maturity function, the setting behavior, apparent activation energy, and rate constant of the prepared mixtures were also measured. This study reveals that the compressive strength development of HSC cured at the reference temperature for an early age of 3 days is insignificantly affected by the subsequent curing temperature histories. The proposed maturity approach with the modified equivalent age accurately predicts the strength development of HSC.

Compressive Strength Development of High-Strength Concrete under Different Curing Temperatures

The present study examined the in-place strength of high-strength concrete based on the relative strength-maturity relationship. The measured strength gain of high-strength concrete was compared with the predictions obtained from the modified maturity function to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. This study demonstrates that the compressive strength gain of concrete cured at the reference temperature (20°C) for an early age of 3 days is little affected by the subsequent curing temperature histories.

Influence of Metakaolin in High Strength Concrete of M70 Grade for Various Temperatures and Acidic Medium

Concrete made of cement is the most adaptive material for construction purpose. Design and Preparation of such a concrete mix with good strength and durability has been always the need of the day. Use of mineral admixture in concrete mix has made a remarkable achievement in development and design of high strength concrete. Among many mineral admixtures available, Metakaolin (MK) is a mineral admixture, whose potential is not yet fully tested and only limited studies have been carried out in India on the use of MK for the development of high strength concrete. MK is a supplementary cementations material derived from heat treatment of natural deposits of kaolin. MK shows high pozzolanic reactivity due to their amorphous structure and high surface area. In this present study Metakaolin is replaced with 0, 10, 15, 20, 25 and 30 % of cement to observe the compressive strength of M70 grade concrete. Conclusions are made from the various results and the discussions there on to identify the effect of partial replacement of cement by MK in the design concrete mix. The results conclude that, the use of Metakaolin Concrete (MKC) has improved the performance of concrete under various conditions

Real-time strength development monitoring for concrete structures using wired and wireless electro-mechanical impedance techniques

The demand for the construction of high-rise buildings and wide-span bridges using High Strength Concrete (HSC) has increased. To prevent unexpected collapse during and after the construction of HSC structures, it is essential to confirm the strength development of HSC during the curing process. In this study, a novel method to estimate the strength development of HSC based on Electromechanical Impedance (EMI) measurements using a wireless sensor node is proposed. The EMI of HSC structures with 100 MPa strength was tracked to monitor the strength development. In addition, two types of signal processing, resonant frequency shift and cross-correlation coefficient were applied in sequence to examine the trend of the impedance variations more quantitatively. The results confirmed that the proposed technique can be applied successfully to more reliable and economical monitoring of the strength development during the curing process of HSC structures.

The Effect of Curing Conditions (In Situ vs. Laboratory) on Compressive Strength Development of High Strength Concrete

During the construction of the bridge near Štrba village, concrete was needed to achieve the cube strength of 35N/mm2 after 48hours to allow the prestressing works. However, the question remained how to practically verify the real strength achieved in the structure after such a short time. Whereas the specimens were cured in accordance with valid standards at 20°C in water, it was doubtful whether the real strength of the concrete structure, which is hardening at ambient temperatures around 2°C, corresponds to these measured strengths. It was questionable how to cure the specimens to get as close to the real strengths as possible.

Strength Development, Toughness and Fire Resistive Performance of 150 to 200N/mm2 Super-High Strength, High Performance Concrete

Super high strength concrete with compressive strength of 150 to 200N/mm2 using hybrid fiber reinforcement of organic and steel fiber was developed. Properties of fluidity of fresh concrete and effect of curing condition on strength development were studied. Viscosity of fresh concrete was significantly reduced by newly developed Maleate polycarboxylate-based superplasticizer. Strength development of high strength concrete was enhanced by high temperature steam curing. Hybrid fiber reinforcement was effective to improve toughness and fire resistance of super high strength concrete. The higher the aspect ratio and tensile strength of steel fiber, the higher the toughness of concrete became. Hybrid fiber reinforcement enables to reduce spalling and to maintain fire resistance for 3 hours in super high strength concrete columns.

A Fundamental Study on Concrete Substituted Cement with Industrial By-Products

In this research, we have carried out the fundamental research on development of high strength concrete using the powder combining three industrial by-products as substitute of cement. The by-products used were fly ash of type II, ground granulated blast-furnace slag and gypsum. As a result,-it was possible to make a high strength paste, using vibrating compaction, with a water-powder ratio of 25%, The paste had compressive strength greater than 60 N/mm2 after curing for 91 days. Further we found it was possible to make high strength concrete of varying sand-aggregate ratios which all had a compressive strength of about 30 N/mm2 after curing for 28 days and 40 N/mm2 after curing for 91 days. Finally we obtained the optimum mixture proportion of concrete is unit water content = 170 kg/m3, water-powder ratio = 25%, and sand-aggregate ratio = 40%, For each of these results no cement was used.

Break-Off Test for High-Strength Concrete

Abstract High-strength concrete is one of the new developments in concrete technology. In addition to compressive strength levels above 60 MPa, high workability, improvements in early age performance and durability appear to be its main advantages. This paper studies the suitability of the break-off test to evaluate strength development of high-strength concrete. Regression equations between break-off pressure and compressive strength were calculated. The effects of different variables such as age, type of coarse aggregate, and strength level are discussed. The obtained results indicate that the break-off test can be used satisfactorily to evaluate the quality of concretes with compressive strength levels up to 100 MPa.